ASIC currents in cultured primate retinal rod and cone cells

Acid Sensing Ion Channels (ASICs) are widely expressed in the nervous system and involved in an increasing number of functions such as nociception, mechanoreception, and taste transduction, to name a few. In the CNS, ASICs are involved in synaptic plasticity, learning/memory, and in acidosis-mediated neuronal injury. In retina, ASICs are expressed in rodent, rabbit and monkey retina and pharmacological and gene knockdown studies have indicated changes in the earliest phases of electroretinogram that point to effects on phototransduction. This finding led us to investigate the electrophysiological/pharmacological properties of ASICs in cultured primate rod and cone cells. Patch-clamp recordings showed transient ASIC currents with a threshold pH of ~ 7.0 and pH_0.5 of 6.15 ± 0.03 and 6.33 ± 0.03 for cultured rod and cone cells, respectively. The currents were almost completely blocked by amiloride and highly sensitive to PcTx-1. Our results for the first time demonstrate the expression of functional ASICs on primate photoreceptors and suggest that ASIC currents in these cells are mediated predominantly by homomeric ASIC1a channels.